Cooling water process control system

ABSTRACT

A cooling system uses a closed circuit cooling tower in series with a chiller to either lower the chiller operating point or completely cool the chill water without use of the chiller, depending on weather conditions. The process and system expands the entire function of the cooling process with a control system design that examines the power consumed by all the devices of the system, the actual load being introduced into the system, water temperatures, and weather conditions, and makes decisions based on performance criteria through the control device&#39;s program algorithms.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of U.S. provisionalapplication number 61/755,433, filed Jan. 22, 2013, the contents ofwhich are herein incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to cooling processes and systems and, moreparticularly, to the use of closed circuit cooling tower to either lowerthe chiller operating point or completely cool without use of thechiller, depending on weather conditions.

Water chillers are often used to provide mechanical cooling to abuilding, data center, industrial process, or the like. Conventionalchillers provide mechanical cooling by removing 100% of the heat loadfrom the water. These systems have heat exchangers and require multiplepumps. The conventional systems can create delta temperature losses thatdecrease overall system efficiency.

As can be seen, there is a need for an improved cooling process andsystem that can selectively take advantage of water tower cooling whenfeasible.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a cooling system comprises oneor more chillers; one or more closed circuit cooling towers in serieswith the one or more chillers; and a controller operable to utilize theclosed circuit cooling towers as a pre-cooling device to lower anoperating point by reducing a heat load to the one or more chillers, thecontroller further operable to use only the one or more closed circuitcooling towers, shutting down the one or more chillers, when the heatload can be removed by the one or more closed circuit cooling towers.

In another aspect of the present invention, a method for operating acooling system comprises utilizing one or more closed circuit coolingtowers in one of three operation states, a first operation state wherethe closed circuit cooling tower is used as a pre-cooling device tolower an operating point by reducing a heat load of chill water to oneor more chillers, a second operation state where the closed circuitcooling tower is used to remove the heat load from chill water and thechill water is used directly to a load, without using the one or morechillers, and a third operation state where the closed circuit coolingtower is used to adjust a water flow to have the cooling tower create afalse load and the chiller is adjusted to a less kilowatt per ton (kW/T)operating point; and controlling the operation state of the one or morechillers with a controller.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdrawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWING

The Figure is a schematic representation of a cooling water processcontrol system according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is of the best currently contemplatedmodes of carrying out exemplary embodiments of the invention. Thedescription is not to be taken in a limiting sense, but is made merelyfor the purpose of illustrating the general principles of the invention,since the scope of the invention is best defined by the appended claims.

Broadly, an embodiment of the present invention provides a coolingsystem using a closed circuit cooling tower in series with a chiller toeither lower the chiller operating point or completely cool the chillwater without use of the chiller, depending on weather conditions.Conventional water side economizers do not use the tower water in serieswith the chillers. The process and system of the present inventionexpands the entire function of the cooling process with a control systemdesign that examines the power consumed by all the devices of thesystem, the actual load being introduced into the system, watertemperatures, and weather conditions, and makes decisions based onperformance criteria through the control device's program algorithms.

Referring now to the Figure, the process and system of the presentinvention uses cooling towers 12 as energy balance control, via thecontrol system, to either (1) divert the return water flow 20 from theload (not shown) through a tower 12 first, then through the evaporatorof the chiller 10, effectively reducing the load to the chiller(s), or(2) divert the return water flow 20 from the load through only the tower12 to cool the entire load, without using the chiller(s) 12, byby-passing the chillers(s) 12 while monitoring all data points to makeoperating decisions.

A process controller 14 used in the present invention can assess thekilowatt per ton of the chiller(s), pumps, fans, water temperature, andthe like, and, if the load reduces to a point that the cost to operatethe chiller(s) is more kilowatts per ton (kW/T), then the controllerwill adjust the water flow to have the towers create a false load,adjusting the chiller(s) to a less kW/T operating point that, in mostcases, is a higher capacity percentage, but lower kW/T. When conditionsare correct, the chiller(s) can be taken out of operation, along withcondenser water pumps, and only the towers and the chill water pumps(not shown) will operate and, at reduced kW/T load points, whilecontrolling the water results to the load. Using the closed circuitcooling towers allows for precise water chemistry treatment to allow thewater to be used as a direct coupled process to all devices.

The Figure shows an exemplary wall 22 that separates the inside from theoutside. This wall 22 can be located at various locations and is notmeant to be disposed adjacent to the chiller 10 and the cooling towers12.

Magnetic chillers 10 can be used as the primary cooling source, untilweather conditions allow, then the cooling towers 12 can act as apre-cooling device to lower the operating point of the chiller 10 byreducing the heat load to the chiller 10, allowing the chiller 10 tooperate at its most efficient point as possible at all times. Kilowattmeters can be used to reflect the operating point and control systemscan be used to determine the positions of the valves V1-V15 to separatethe closed circuit cooling towers 12 to do different functions forcondenser heat rejection and evaporator pre-cooling heat reduction tothe chillers 10.

In some cases, the cooling towers 12 can be used to completely cool thechillers 10, where the condenser pumps 24 can be turned off, but left ina rapid restart mode, if needed to be turned back on to handle a higherheat load, or if weather conditions change such that the cooling towers12 can no longer handle the required heat load.

The system of the present invention includes one or more magneticchillers (one is shown in the Figure, but any number can be used,depending on the system design, heat load needs, and the like). Otherstyles of chillers can be used instead of or in addition to magneticchillers. The system further includes one or more closed circuit coolingtowers 12. The Figure shows two cooling towers 12 connected in parallelwith each other (and in series with the chiller); however, the systemcould use any number of cooling towers.

The system of the present invention also includes various measurementand flow control devices, such as actuator controlled valves V1-V15, wetbulb calibrated sensors, insert water sensors, kilowatt meters, pressuretransducers, variable frequency drives (for tower fans, condenser andchill water pumps, for example), piping special configurations andcontrol engineering programming data with fail safe devices formaintaining normal operating demand.

The valves V1-V15 can be used to provide the most efficient operation ofthe system. For example, the valves can be used to control whether chillwater or condenser water flows through each of the cooling towers 12.The valves V1-V15 can also be used to control whether chill water passesthrough the chiller 10, or if the cooling towers 12 alone providessufficient cooling to deliver this cooling water chilled water directlyto the load.

To use the present invention, heat load requirements and safety factorscan be established and the optimal magnetic chillers (or other chillertype) and closed circuit cooling towers can be chosen for theapplication. Climate performance data can be plotted and piping can beconfigured to perform all functions, from the towers to the chiller,both evaporator and condenser functions, together and separately. Valvescan be used to actuate against the pressure differential of the systempumps. Wet bulbs, entering and leaving water temperature, pressuredifferentials, and kW/T data for all functions can be gathered tocontrol the process function for the most efficiency at all times.Transducers can be used to operate variable frequency drives (VFDs) tocontrol pumps and kilowatt meters can be used to monitor all devices forcomparison to the reflected load gathered by flow stations reporting theload conditions.

The system and process of the present invention can be used in office,data centers, and manufacturing industries on a broad spectrum. Thesystem and process of the present invention can be easily adapted tovarious real world needs and can be scaled accordingly. The system andprocess of the present invention can reduce kW/T loads, effectivelyreducing operating cost. Combined with potential load shed methodology,the peak load reduction is a viable solution for the customer to avoidthe higher demand load kilowatt-hour cost.

In some embodiments of the present invention, a geothermal addition anda dedicated reheat system addition can be used to enhance the processand provide heating water. In some embodiments, magnetic bearingchillers can do the reheat function via a separate water loop for theheating water and supplemental piping to the chill water loop. Thegeothermal loop can help remove heat from the system, both condenserwater and chill water, to increase the useful hours of supplementalcooling.

It should be understood, of course, that the foregoing relates toexemplary embodiments of the invention and that modifications may bemade without departing from the spirit and scope of the invention as setforth in the following claims.

What is claimed is:
 1. A cooling system comprising: one or morechillers; one or more closed circuit cooling towers in series with theone or more chillers; and a controller operable to utilize the closedcircuit cooling towers as a pre-cooling device to lower an operatingpoint by reducing a heat load to the one or more chillers, thecontroller further operable to use only the one or more closed circuitcooling towers, shutting down the one or more chillers, when the heatload can be removed by the one or more closed circuit cooling towers. 2.The cooling system of claim 1, further comprising a plurality ofactuator driven valves receiving commands from the controller to controlflow of condenser fluid and chill fluid through the cooling system. 3.The cooling system of claim 1, wherein the controller receives inputfrom a plurality of sensors to determine an operation state thatprovides optimal energy efficiency.
 4. The cooling system of claim 1,wherein the plurality of sensors include wet bulbs, entering and leavingwater temperature sensors, pressure differential sensors, and weathercondition sensors.
 5. A method for operating a cooling system,comprising: utilizing one or more closed circuit cooling towers in oneof three operation states, a first operation state where the closedcircuit cooling tower is used as a pre-cooling device to lower anoperating point by reducing a heat load of chill water to one or morechillers, a second operation state where the closed circuit coolingtower is used to remove the heat load from chill water and the chillwater is used directly to a load, without using the one or morechillers, and a third operation state where the closed circuit coolingtower is used to adjust water flow to have the cooling tower create afalse load, allowing the one or more chillers to be adjusted to a lesskilowatt per ton (kW/T) operating point; and controlling the operationstate of the one or more chillers with a controller.
 6. The method ofclaim 5, further comprising controlling a plurality of actuator drivenvalves that receive commands from the controller to control flow ofcondenser fluid and chill fluid through the cooling system.
 7. Themethod of claim 5, further comprising receiving input from a pluralityof sensors to determine an operation state that provides optimal energyefficiency.
 8. The method of claim 7, wherein the plurality of sensorsinclude wet bulbs, entering and leaving water temperature sensors,pressure differential sensors, and weather condition sensors.